The present invention relates to powder material transportation apparatus for transporting powder materials by a rotating member, such as a coil or a spiral blade, in its axial direction and more particularly to powder transportation apparatus for transporting powder developer, for use in cleaning apparatus or development apparatus of electrophotographic copying machines or of electrostatic recording machines.
In electrophotographic copying or electrostatic recording machines, latent electrostatic images formed on a photoconductor or on a dielectric material are developed by color fine powder called toner and the resulting toner images are transferred to plain paper to obtain copies. After image transfer, toner remains on the surface of the toner image bearing member, and the remaining toner has to be removed for the next copying cycle. A toner cleaning apparatus is used for performing such cleaning.
Conventionally, the toner cleaning apparatus includes a cleaning member, which contact the surface of a toner image bearing member to remove the remaining toner therefrom, and discharging apparatus for discharging the removed toner out of the toner cleaning apparatus. The discharging apparatus comprises a rotating member such as a coil or a spiral blade and is disposed near the bottom of a housing unit which is gradually narrowed in the direction of the bottom. The toner collected by the cleaning member is caused to drop into a bottom portion of the housing unit and is then discharged out of the housing unit by the discharging apparatus. In this type of cleaning apparatus when the fluidity of toner is reduced during the continuous operation of the apparatus or by some change of the ambient conditions, the toner graudually deposits and accumulates on the opposite inner walls of the housing unit, right above the discharging apparatus. As a result, a toner bridge is formed between the walls. When such a toner bridge is formed, the discharging apparatus runs idly in a vacant portion under the toner bridge and newly collected toner is piled on the bridge with the result that the collected toner overflows from the housing unit, smearing various parts of the copying machine or copies due to insufficient cleaning.
Toner removed from the surface of a photoconductor drum by a cleaning blade drops all over a transportation coil disposed at a bottom portion of the housing unit. Since the transportation coil has an equal pitch and an equal diameter along its length, it has a uniform toner transportation capacity over its entire length. However, since the transportation coil transports toner in its axial direction, toner is gradually accumulated near an outlet portion of the cleaning apparatus. This is because the amount of toner to be transported increases in the downstream direction of the transportation coil although the transportation capacity is equal in each segment of the transportation coil. When a certain amount of developer is accumulated near the outlet portion of the cleaning apparatus, a toner bridge is formed likewise and a vacant portion is formed in which the transportation coil is operated without transporting toner thereby.